1. Field of the Invention
This invention relates to the inspection of translucent containers for the presence of extraneous matter and/or cracks and in particular to a light collection apparatus suitable for use with the invention of my co-pending patent application Ser. No. 483,350 filed June 26, 1974.
2. Description of the Prior Art
It is known to use fiber optic elements in bottle inspection and the like apparatus. In German Offenlegungsschrift No. 1,473,749 there is described test and inspection equipment for glass containers in which the light receiving or collection elements of the said apparatus includes a light conducting device formed from a number of glass fiber optic elements. There are however, certain problems in the use of glass fiber optic elements in the manner described in this German Offenlegungsschrift No. 1,473,749. These arise when the area over which light must be collected is large in comparison with the light sensitive area of the photodetector used. It will be appreciated for example that if it is necessary to collect light over an area of for example 20 cms .times. 50 cms. i.e. 1,000 sq. cms. and to transmit this light to a photodetector such as a photo multiplier tube having a total light sensitive area of maybe 20 sq. cms., it is impossible to do so by means of a bundle of closely packed fiber otpic elements. If the number of fiber optic elements is reduced so as to be compatible with the light sensitive area of the photo multiplier tube the number and spacing of the fiber optic elements in the area 20 cms. by 50 cms.will be inadequate for effective light collection. It will be appreciated that it is essential that all the light impinging on the light collection apparatus be collected. Further it is apparent that the effectiveness of the light collection element of the apparatus is central to the operation of the inspection apparatus. While photo multiplier tubes have the necessary characteristics for use in such inspection machines, they have in general a photo-sensitive area which is of limited size and considerably smaller than the area over which light collection must be provided. If however, fiber optic elements are used in the manner described in German Offenlegungsschrift No. 1,473,749 the problem of the size of the photo-sensitive area of the photo-electric cell is not overcome.